EP0351915B1 - Starting-up the timing in a device for deriving a clock signal - Google Patents

Starting-up the timing in a device for deriving a clock signal Download PDF

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Publication number
EP0351915B1
EP0351915B1 EP89201869A EP89201869A EP0351915B1 EP 0351915 B1 EP0351915 B1 EP 0351915B1 EP 89201869 A EP89201869 A EP 89201869A EP 89201869 A EP89201869 A EP 89201869A EP 0351915 B1 EP0351915 B1 EP 0351915B1
Authority
EP
European Patent Office
Prior art keywords
signal
code
word
switching means
control
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP89201869A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0351915A1 (en
Inventor
Johannes Bernardus Horsten
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Gloeilampenfabrieken NV
Priority to AT89201869T priority Critical patent/ATE95368T1/de
Publication of EP0351915A1 publication Critical patent/EP0351915A1/en
Application granted granted Critical
Publication of EP0351915B1 publication Critical patent/EP0351915B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N11/00—Colour television systems
    • H04N11/06—Transmission systems characterised by the manner in which the individual colour picture signal components are combined
    • H04N11/08—Transmission systems characterised by the manner in which the individual colour picture signal components are combined using sequential signals only
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N7/00—Television systems
    • H04N7/08—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division
    • H04N7/083—Systems for the simultaneous or sequential transmission of more than one television signal, e.g. additional information signals, the signals occupying wholly or partially the same frequency band, e.g. by time division with signal insertion during the vertical and the horizontal blanking interval, e.g. MAC data signals
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N5/00—Details of television systems
    • H04N5/76—Television signal recording
    • H04N5/91—Television signal processing therefor
    • H04N5/93—Regeneration of the television signal or of selected parts thereof
    • H04N5/932—Regeneration of analogue synchronisation signals

Definitions

  • the invention relates to a device for deriving a clock signal from an electric signal, the electric signal being made up of consecutive signal blocks, a signal block comprising a first block section containing a first signal and a second block section containing a second signal, the first block section of every n-th signal block containing a unique code-word, the device comprising an input terminal for receiving the electric signal, which input terminal is coupled to a first terminal of switching means, which have a second terminal coupled to an input of a phase-locked loop and to an input of a code-word detector which is constructedto detect the unique code-word, the output of the code-word detector being coupled to a control-signal generator, which has an output coupled to a control-signal input of the switching means, the control-signal generator being constructed to generate a control-signal during the time that first block sections are applied to the first terminal of the switching means, and the switching means being constructed to couple the first terminal to the second terminal under the influence of the control-signal.
  • Such a device is employed inter alia in video recorders in order to derive the clock signal from a video signal, for example a MAC signal, read from a magnetic record carrier.
  • the device may also be employed in the recording mode of a video recorder when the clock signal is derived from the incoming signal.
  • the MAC (multiplexed analog components) signals are signals comprising a sequence of lines (signal blocks) with a first block section containing a line-synchronising signal and a second block section containing the chrominance and luminance information of the video signal.
  • the first block sections further contain additional signals, such as for example the audio signal and other data.
  • the first block sections in the MAC signals generally contain digitally encoded signals
  • the chrominance and luminance information in the second block sections generally takes the form of an analog signal.
  • One line (signal block) in the MAC signal has a length of 64 ⁇ s and the first and the second signal blocks have a length of slightly over 10 ⁇ s and slightly less than 54 ⁇ s.
  • the first block section of every n-th signal block i.e. every 625-th signal block for the MAC signal, contains a unique code-word. This may mean that in addition to the signal already present in the first block section a unique code-word is included in this block section. Another possibility is that the signal present in this block section takes the form of the unique code-word.
  • the relevant signal block which includes the unique code-word corresponds to the 625-th and last video line in the MAC video signal which represents exactly one video picture.
  • the television picture has a higher resolution, the sound is of a higher quality, and there is (hardly) any crosstalk between chrominance and luminance signal.
  • This last-mentioned advantage is obtained because the chrominance information and the luminance information are stored separately in a second block section.
  • the phase-locked loop (PLL) in the known device derives the clock signal from the signal content of the first block sections, which for this purpose are applied to the input of the PLL. To this end the switching means are closed at the instants at which the first block sections are applied to the first terminal, i.e. the terminals 1 and 2 are interconnected, and at other instants the switching means are open.
  • the clock signal is derived by means of a "gated PLL". Such a method of deriving the clock signal is known.
  • a circuit for performing a similar method is known from EP-A-0 250 274.
  • the device in accordance with the invention is characterized in that the switching means further comprise a third terminal, which third terminal is also coupled to inputs of the phase-locked loop and the code-word detector via a high-pass filter, in that the control-signal generator is operable to generate a second control-signal at the instant at which the device is turned on, in that the switching means are adapted to couple the first terminal to the third terminal under the influence of the second control-signal, and in that the control-signal generator is adapted to terminate the second control-signal after detection of a unique code-word by the code-word detector, and that the high-pass filter has a cut-off frequency smaller than the bit rate of the unique code word.
  • the invention is based on the recognition of the fact that at the instant at which the device is turned on it takes a comparatively long time for a phase-locked loop of the gated type to lock in. This is because the timing is not correct until a unique code-word has been detected.
  • the time window cannot be defined accurately enough to gate out the information in the first block section. Consequently, the clock signal cannot be derived adjusted, so that detection of a unique code-word in the code-word detector, which (also) requires the clock signal to sample the signal applied to the input, is rather difficult.
  • the high-pass filter produces a bandwidth limitation in the electric signal, which reduces the (adverse effect of) noise. Moreover, a d.c. free signal is now applied to the code-word detector, so that detection of the unique code-word is simplified.
  • the phase-locked loop After detection of the unique code-word the phase-locked loop is in lock and the time window can be opened at the correct instant. This means that now it is possible to change over to the gated PLL function, which ensures that only information in the first block sections is transferred to the PLL and the code-word detector.
  • Fig. 1 shows the device, comprising an input terminal 1 coupled to the first terminal 2 of the switching means 3, for example in the form of a three-position switch.
  • the switching means 3 comprise a second terminal 4, coupled to inputs of a phase-locked loop 5 and a code-word detector 6.
  • a third terminal 7 of the switching means 3 is coupled to the inputs of the phase-locked loop 5 and the code-word detector 6 via a high-pass filter 8.
  • the switch S Under the influence of control-signals applied to the switching means 3 via the control-signal input 9 the switch S can be set to the upper position, the centre position, or the lower position.
  • the output of the phase-locked loop 5 is a clock signal, which is applied to an output terminal 10.
  • the code-word detector 6 also receives the clock signal via the input 11. This clock signal is required for detection of the code-word.
  • the output 13 of the detector 6 is coupled to an input 14 of a control-signal generator 15. Its output 16 of this generator is coupled to the control-signal input 9 of the switching means 3.
  • the electric signal applied to the input terminal 1 is shown very diagrammatically in Fig. 2a.
  • the signal comprises successive signal blocks, such as the block B i in Fig. 2a.
  • Each signal block B i comprises a first block section EBD i and a second block section TBD i .
  • the first block section EBD i contains a first signal.
  • the signal block B i-1 in Fig. 2a contains a unique code-word CW, which is stored in the first block section EBD i-1 of the signal block B i-1 .
  • the unique code-word may be, for example, a digital number comprising a unique combination of "ones" and "zeros'.
  • the second block section of a signal block contains a second signal.
  • the signal information in the first block section EBD of a signal block is digital and generally comprises audio information and a line-synchronising signal.
  • the first block section of the signal block B i-1 contains the unique code-word CW. It is assumed that the first block section EBD i-1 of the signal block B i-1 only contains this unique code-word.
  • the first block sections EBD i+n-1 EBD i+2n-1 , ... etc. also comprise (only) said unique code-word.
  • the chrominance information and the luminance information of a video line in a video picture are stored separately one after the other.
  • the operation of the device shown in Fig. 1 will now be explained with reference to Fig. 2, which shows the signal waveforms.
  • the device shown in Fig. 1 may be incorporated in, for example, a video recorder, for generating a clock signal read from the record carrier in the playback mode, in particular from the signal information in the first block sections EBD of the signal read from the record carrier.
  • the control-signal generator 15 generates a second control-signal for the switching means 3, under the influence of which the switching means are set to the upper position (position I, see Fig. 1 and Fig. 2c).
  • the complete signal is applied to the inputs of the phase-locked loop 5 and the code-word detector 6 via the high-pass filter 8.
  • the phase-locked loop then supplies a clock signal.
  • This clock signal will have substantially the desired value but this value will not yet be accurate enough since the loop 5 has not yet locked incorrectly to the signal information in the first block sections. This means that the clock instants at which the (digital) signal applied to the input 12 is sampled in the code-word detector 6 will not be timed correctly.
  • the correct timing is maintained because the code-word detector 6 each time detects consecutive code-words in the first block sections EBD i+n-1 , EBD i+2n-1 , ... etc., which are also transferred to the code-word detector 6 by the gate formed by the switching means 3 and, if required, the control-signal generator adapts the timing accordingly.
  • this high-pass filter must have a (low) cut-off frequency smaller than the bit rate of the unique code-word. In fact, this also means that the cut-off frequency of the high-pass filter should be smaller than the bit rate of the first signal.
  • the phase-locked loop 5 can then already generate a clock signal in this time interval t0, t3.
  • the first signal may be for example a duobinary signal, as is described in the Applicant's prior Netherlands Patent Application no. 8801704 (PHN 12.618).
  • the clock signal can be derived by means of the device described in said Netherlands Patent Application in the element bearing the reference numeral 5 in Fig. 1.
  • the invention is not limited to the embodiment shown herein.
  • the invention also relates to those embodiments which differ from the embodiment disclosed herein in respects which are not relevant to the inventive idea.
  • the electric signal need not necessarily be a MAC signal.
  • the electric signal may alternatively be, for example, a MUSE signal.
  • the code-word detector may further be adapted to count the number of times that no code-word is detected during the occurrence of a time window.
  • the code-word detector 6 has counted n times that no code-word was detected, it is assumed that the "timing" is lost.
  • the code-word detector 6 now generates a control-signal at its output 13 which is sent to the switch S. Under the influence of this control-signal, the switch S switches over to the position I in order to re-establish timing in the way as previously described.

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Power Engineering (AREA)
  • Synchronisation In Digital Transmission Systems (AREA)
  • Television Signal Processing For Recording (AREA)
  • Stabilization Of Oscillater, Synchronisation, Frequency Synthesizers (AREA)
  • Synchronizing For Television (AREA)
EP89201869A 1988-07-21 1989-07-17 Starting-up the timing in a device for deriving a clock signal Expired - Lifetime EP0351915B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT89201869T ATE95368T1 (de) 1988-07-21 1989-07-17 Starten der zeitsynchronisierung in einer anordnung zum ableiten eines taktimpulssignals.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL8801844 1988-07-21
NL8801844A NL8801844A (nl) 1988-07-21 1988-07-21 Opstarten van de timing in een inrichting voor het afleiden van een kloksignaal.

Publications (2)

Publication Number Publication Date
EP0351915A1 EP0351915A1 (en) 1990-01-24
EP0351915B1 true EP0351915B1 (en) 1993-09-29

Family

ID=19852658

Family Applications (1)

Application Number Title Priority Date Filing Date
EP89201869A Expired - Lifetime EP0351915B1 (en) 1988-07-21 1989-07-17 Starting-up the timing in a device for deriving a clock signal

Country Status (8)

Country Link
US (1) US4975928A (ja)
EP (1) EP0351915B1 (ja)
JP (1) JP2585802B2 (ja)
KR (1) KR0144458B1 (ja)
AT (1) ATE95368T1 (ja)
DE (1) DE68909530T2 (ja)
ES (1) ES2045388T3 (ja)
NL (1) NL8801844A (ja)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2374553A1 (en) 2010-04-12 2011-10-12 OSCAM S.p.A. Plant for bending metal bars with automatic loading of the bars, and loading method used in said plant

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5235620A (en) * 1988-10-27 1993-08-10 Canon Kabushiki Kaisha Information signal demodulating apparatus
JP2548989B2 (ja) * 1989-09-20 1996-10-30 日本ビクター株式会社 デジタル記録再生装置

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5665530A (en) * 1979-10-31 1981-06-03 Sony Corp Pll circuit
ZA873823B (en) * 1986-06-03 1988-01-27 Scientific Atlanta Improving immunity to channel distortions of mac signal
JPH0666705B2 (ja) * 1987-01-12 1994-08-24 日本電気株式会社 間欠受信回路
EP0250274B1 (fr) * 1987-03-19 1992-12-30 France Telecom Procédé et dispositif de modulation de signaux de télévision, notamment du type D2-MAC/Paquet

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2374553A1 (en) 2010-04-12 2011-10-12 OSCAM S.p.A. Plant for bending metal bars with automatic loading of the bars, and loading method used in said plant

Also Published As

Publication number Publication date
KR0144458B1 (ko) 1998-07-15
DE68909530T2 (de) 1994-03-24
KR900002642A (ko) 1990-02-28
JPH0273789A (ja) 1990-03-13
ES2045388T3 (es) 1994-01-16
DE68909530D1 (de) 1993-11-04
JP2585802B2 (ja) 1997-02-26
NL8801844A (nl) 1990-02-16
US4975928A (en) 1990-12-04
ATE95368T1 (de) 1993-10-15
EP0351915A1 (en) 1990-01-24

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